The present invention relates to a sintered carbonitride alloy with titanium as the main component which simultaneously has obtained improved toughness behavior and increased wear resistance and resistance against plastic deformation.
Classic cemented carbide, i.e., based on tungsten carbide (WC) and cobalt (Co) as binder phase, has in the last few years met increased competition from titaniumbased hard materials, usually called cermets. In the beginning, these alloys were used only for extreme finishing due to their extraordinary wear resistance at high cutting temperatures. This property depends primarily upon the good chemical stability of these titanium alloys. The toughness behavior and the resistance against plastic deformation were not satisfactory however, and therefore the area of application was relatively limited.
Development has, however, proceeded and the area of application for titanium-based hard material has been considerably enlarged. The toughness behavior and the resistance to plastic deformation has been considerably improved. This has been done, however, by partly sacrificing the wear resistance.
Besides titanium, the other metals from groups IVa, Va and VIa of the periodic table, i.e., Zr, Hf, V, Nb, Ta, Cr, Mo and/or W are normally used as hard constituent formers generally as carbides, nitrides and/or carbonitrides. The grain size of the hard constituents is generally &lt;1 .mu.m. As binder phase nowadays often both cobalt and nickel are used. The amount of binder phase is generally 3-25 weight %.
During sintering, the relatively less stable hard constituents are dissolved in the binder phase and precipitate then as a rim on the more stable hard constituents. A very common structure in alloys in question is therefore hard constituent grains with a core-rim structure. A patent in this area is U.S. Pat. No. 3,971,656 which comprises Ti- and N-rich cores surrounded by rims rich in Mo, W and C. Through U.S. patent application Ser. No. 07/543,474 (our reference: 024000-757), it is known that at least two different combinations of duplex core-rim structures in well-balanced proportions give optimal properties with regard to wear resistance, toughness behavior and/or resistance against plastic deformation. Further examples of patents in this area are U.S. Pat. Nos. 4,904,445; 4,775,521; and 4,957,548.